PART IV.

NIGHT AND DAY MOVEMENTS IN PLANTS.

XLVI.--DIURNAL MOVEMENTS IN PLANTS.

Complexity of the problem--The different factors involved-- Autonomous movements--Epinasty and hyponasty--Positive and negative thermonasty--Thermo-geotropism--Classification of diurnal movements--Discriminating tests for classification-- Diurnal variation of light and of temperature 523

XLVII.--DIURNAL MOVEMENT DUE TO ALTERNATION OF LIGHT AND DARKNESS.

Experimental arrangements--The Quadruplex Nyctitropic Recorder--Diurnal movement of the leaflet of _Cassia alata_---Effect of variation of temperature--Effect of variation of light--Diurnal movement of the terminal leaflet of _Desmodium gyrans_--The 'midday sleep' 535

XLVIII.--DIURNAL MOVEMENT DUE TO VARIATION OF TEMPERATURE AFFECTING GROWTH.

Tropic and nastic movements--Distinction between thermonastic and thermo-geotropic action--Diurnal movement of _Nymphæa_--Action of light--Effect of variation of temperature 546

XLIX.--DAILY MOVEMENT IN PLANTS DUE TO THERMO-GEOTROPISM.

Characteristics of thermo-geotropic movements--Diurnal movement of Palm trees--Diurnal movement of procumbent stems and of leaves--Continuous diurnal record for successive thermal noon--Modification of the diurnal curve--Effect of fluctuation of temperature--Effect of restricted pliability of the organ--Effect of age--Effect of season--Reversal of the normal rhythm--Effect of constant temperature--Diurnal movement in inverted position 554

L.--THE AFTER-EFFECT OF LIGHT.

Electric after-effect of light--After-effect at pre-maximum, maximum, and post-maximum--Tropic response under light, and its after-effects at pre-maximum, maximum, and post-maximum 569

LI.--THE DIURNAL MOVEMENT OF THE LEAF OF _MIMOSA_.

Four different phases in the diurnal record of _Mimosa_-- Different factors determining its diurnal movement--Diurnal variation of geotropic torsion--Autonomous pulsation of the leaf of _Mimosa_--The Photometric Recorder--Effect of direct light--The evening spasmodic fall of the leaf--Diurnal movement of the amputated petiole--Diurnal curve of the petiole of _Cassia alata_--Response of _Mimosa_ to darkness at different parts of the day--After-effect of light at pre-maximum, maximum, and post-maximum 576

ILLUSTRATIONS.

FIGURE. PAGE.

93. Arrangement for compensation of growth-movement by equal subsidence of plant-holder 257

94. Photograph of the Balanced Crescograph 258

95. Balanced Crescographic record 260

96. Record showing the effect of CO_{2} 265

97. Effect of ether and of chloroform 266

98. Diagrammatic representation of effects of Indirect and Direct stimulation 275

99. Tropic curvature of _Crinum_ 276

100. Turgor variation caused by Indirect stimulation 281

101. Response of _Mimosa_ leaf under transverse transmission of effect of electric stimulus 282

102. Diagrammatic representation of Indirect and Direct stimulation of tendril 290

103. Record by Method of Balance 291

104. Variation of growth under direct stimulation 292

105. Positive curvature of tendril of _Cucurbita_ 295

106. Diagrammatic representation of effects of Indirect and Direct unilateral stimulation of tendril 296

107. Retardation of rate of growth under cathode 303

108. Acceleration of rate of growth under anode 303

109. Thermonastic and radionastic responses of petal of _Zephyranthes_ 308

110. The Thermonastic Recorder 309

111. Negative thermonastic response of _Nymphæa_ 310

112. Successive positive responses of the terminal leaflet of bean plant 317

113. Positive response and recovery under moderate phototropic stimulation 318

114. Persistent positive curvature under stronger stimulation 318

115. Immediate and after-effect of stimulus of light on growth 320

116. Latent period for photic stimulation 324

117. Effect of a single electric spark on growth 325

118. Responses of _Mimosa_ leaf to light from above 330

119. Responses of _Mimosa_ leaf to light from below 330

120. Record of effect of continuous application of light on upper half of pulvinus of _Mimosa_ 331

121. Positive and negative phototropic response of _Oryza_ 335

122. Leaf of _Desmodium gyrans_ 339

123. The Oscillating Recorder 340

124. Tropic effect of increasing intensity of light on the leaflet of _Desmodium gyrans_ 341

125. Tropic effect of increasing intensity of light on growing organ (_Crinum_) 341

126. The Collimator 342

127. Effect of angle of inclination of light on tropic curvature of pulvinated organ 343

128. Effect of angle of inclination on growth-curvature 343

129. Effect of increasing duration of exposure to light 344

130. Effect of continuous electric and photic stimulation on rate of growth 348

131. Characteristic curve of iron 351

132. Simple characteristic curve of phototropic reaction 351

133. Complete phototropic curve of pulvinated organ 358

134. Complete phototropic curve of growing organ 359

135. Arrangement for local application of light 367

136. Response of seedling of _Setaria_ to light 368

137. Effect of application of light to the growing hypocotyl of _Setaria_ 370

138. Response to direct and indirect photic stimulus 373

139. Diagrammatic representation of the effects of direct and indirect stimulation of _Setaria_ 375

140. Photonastic curvature of creeping stem of _Mimosa pudica_ 380

141. Positive phototropic response of _Erythrina indica_ 382

142. Response of leaflet of _Mimosa_ to light 383

143. Response of leaflet of _Averrhoa_ to light 383

144. Diagrammatic representation of different types of phototropic response 384

145. Phototropic curvature of tendril of _Passiflora_ 392

146. Effect of rise of temperature on phototropic curvature 394

147. After-effect of rise of temperature 395

148. Arrangement for record of torsional response 399

149. Record of torsional response of pulvinus of _Mimosa pudica_ 400

150. Leaflets of _Cassia alata_ 404

151. Positive response to thermal radiation 413

152. Record of positive, neutral, and reversed negative curvature under thermal radiation 414

153. Diagrammatic representation of the wireless system 419

154. Mechanical response of _Mimosa_ leaf to electric waves 420

155. Electric response of _Mimosa_ to Hertzian wave 420

156. Record of responses of growing organs to wireless stimulation 422

157. The Quadruplex Geotropic Recorder 428

158. Effect of alternate application of cold on upper and lower sides of the organ 430

159. Geotropic response of flower stalk of Tube-rose 433

160. Geotropic response of _Tropæolum_ 433

161. The Complete Geotropic Curve 435

162. Diagrammatic representation of photic and geotropic stimulation 436

163. The effect of super-imposition of photic stimulus 436

164. Diagrammatic representation of the mechanical and electrical response 443

165. Diagrammatic representation of geo-electric response 447

166. Diagrammatic representation of Methods of Axial and Vertical Rotation 449

167. Diagrammatic representation of the geo-electric response of the shoot 450

168. Geo-electric response of the petiole of _Tropæolum_ 452

169. Geo-electric response of the scape of _Uriclis_ 453

170. Mechanical and electric response to indirect stimulation 463

171. Diagrammatic representation of mechanical and electric response of root 464

172. Diagrammatic representation of geo-electric response of root-tip 469

173. Diagrammatic representation of geo-electric response of growing region of root 471

174. Diagrammatic representation of the geo-perceptive layer 480

175. The Electric Probe 483

176. Transverse section showing continuous geo-perceptive layer (_Bryophyllum_) 488

177. Curve of geo-electric excitation in different layers of _Nymphæa_ 497

178. Curve of geo-electric excitation in _Bryophyllum_ 497

179. Diagram of arrangement of geotropic torsional response 503

180. Additive effect of stimulus of gravity and light 505

181. Algebraical summation of geotropic and phototropic actions 505

182. Comparative balancing effects of white and red lights 506

183. Effect of coal gas on photo-geotropic balance 507

184. Diagram of magnetic balance 511

185. Effect of variation of light on phototropic equilibrium 512

186. Effect of variation of temperature on geotropic torsion 514

187. Simultaneous records of variation of temperature, on up and down movement, and of torsion of the leaf of _Mimosa_ 518

188. Arrest of pulsatory movement of leaflet of _Desmodium gyrans_ by light 528

189. Effect of unilateral light on hyponastic movement 529

190. The Nyctitropic Recorder 537

191. Effect of sudden darkness on leaflet of _Casia alata_ 539

192. Diurnal movement of the leaflet of _Cassia alata_ 540

193. The day and night position of the petiole and terminal leaflet of _Desmodium gyrans_ 541

194. Diurnal record of the terminal leaflet of _Desmodium gyrans_ 542

195. Photograph of closed flower of _Nymphæa_ during day 550

196. Photograph of open flower of _Nymphæa_ at night 550

197. Action of light on the petal of _Nymphæa_ 551

198. Diurnal movement of the petal of _Nymphæa_ 552

199. Diurnal record of the Sijbaria Palm 556

200. Diurnal record of inclined Palm, geotropically curved procumbent stem of _Tropæolum_, and dia-geotropic leaf of Palm 557

201. Diurnal record of leaves of _Dahlia_, _Papya_, and _Croton_ 558

202. Diurnal record of procumbent stem of _Tropæolum_, and leaf of _Dahlia_ for two successive days 560

203. Abolition of the diurnal movement under constant temperature (_Tropæolum_) 565

204. Effect of inversion of plant on diurnal movement of _Tropæolum_ 567

205. Electric response of the leaf stalk of _Bryophyllum_ under light 571

206. Diagrammatic representation of electric after-effect of photic stimulation 571

207. After-effect of pre-maximum photic stimulation 574

208. After-effect of maximum photic stimulation 574

209. After-effect of post-maximum photic stimulation 574

210. Diurnal record of Mimosa in summer and winter 577

211. Record of diurnal variation of torsion in _Mimosa_ leaf 582

212. Continuous record of automatic pulsation of _Mimosa_ leaf 585

213. Photometric record showing variation of intensity of light from morning to evening 586

214. Record of leaf of _Mimosa_ after amputation of sub-petioles 589

215. Diurnal record of _Cassia_ leaf 591

216. Post-maximum after-effect of light on response of leaflet of _Cassia_ 592

217. Effect of periodic alternation of light and darkness on response of _Mimosa_ leaf 594

218. Pre-maximum after-effect of light in _Mimosa_ 595

219. After-effect at maximum 595

220. Post-maximum after-effect exhibiting over-shooting below position of equilibrium 595